1. Field of the Invention
The present invention relates to a cleaning liquid having extremely low corrosiveness to materials such as a metallic film and SOG (Spin On Glass) film and to a process for producing a high quality and highly reliable semiconductor device, said cleaning liquid being suitably used for e.g. removing a deposit polymer formed in the case of dry etching in a semiconductor device production process using silicon, specifically (1) for removing a deposit polymer (deposit protection film) formed and stuck inside or around a via hole (connective hole formed in an insulating film for connecting between a metallic electroconductive film layer formed for wiring in a lower layer of an insulating film and a metallic electroconductive film layer formed in the upper layer of the aforesaid insulating film), which via hole being formed particularly in the insulating layer (interlaminar insulating film); and (2) for removing a deposit polymer formed and stuck to a side wall, etc. after wiring of a metallic electroconductive layer.
2. Description of the Related Arts
In general, lithography has heretofore been adopted in the production of a semiconductor device such as LC and LSI. In the case of producing a semiconductor device by lithography, there are adopted a series of steps of forming an insulating film such as silicon oxide film on a substrate such as a silicon wafer and an electroconductive film such as a metallic film for wiring as electroconduction; uniformly applying a photoresist on the surfaces thereof to provide a photosensitive layer; applying a selective exposure and developing treatment to form a desired resist pattern; subjecting thin films in the lower layer to selective etching treatment using the resist as a mask to form a circuit pattern; and then completely removing the resultant resist pattern.
With recent progress in high integration of semiconductor devices, there is required a pattern formation with an accuracy of a half micron to a quarter micron. Thus, with the progress of such fine processing, the dry etching becomes prevalent in the above-mentioned selective etching treatment and the removal of the resist pattern is carried out increasingly by an ashing treatment with oxygen plasma.
There is known, however, in such a dry etching treatment, the formation of a deposit polymer due to the dry etching gas, resist, processed film and the like in the perimeter of the formed pattern. Such a deposit polymer, when being left inside and around via holes, brings about such unfavorable situations as high electric resistance and short circuit. Accordingly, it is extremely important to remove the deposit polymer in order to obtain a high quality semiconductor device.
The removal of a slight amount of the deposit polymer can be achieved by the combinational use of an ashing treatment and an organic solvent for resist peeling such as an alkaline or acidic solvent. The removal of a large amount thereof can be achieved by a cleaning treatment through the use of a treating liquid containing hydrofluoric acid or containing hydrofluoric acid and ammonium fluoride.
However, such a treatment method by the use of a fluorine compound is useful in the case of using an extremely corrosion resistant insulating film of silicon oxide such as a CVD (Chemical Vapor Deposition)-silicon oxide or a thermal silicon oxide and a relatively corrosion resistant metallic film made of tungsten, titainium, an alloy thereof, titanium/tungsten alloy, titanium nitride or the like, as a lower layer film for the insulating film wherein via holes are formed. Nevertheless, the aforesaid treatment method, when applied to an insulating film of SOG silicon oxide or a metallic film made of aluminium or an aluminum-containing alloy, brings about, for example, a connection failure for the metallic film through via holes by the above-mentioned fluorine compound which corrodes and dissolves the insulating film or the metallic film, thereby completely losing electrical reliability.
In the case where aluminum or an aluminum-containing alloy is subjected to dry etching to form metallic wiring, the deposit polymer is formed and stuck to the side wall of a wiring layer. Such polymer is extremely difficult to remove, and besides an acid is formed by the phenomenon in that radicals and ions in a reaction gas that are incorporated into said deposit polymer are left in the air after the end of the etching treatment, and are reacted with the humidified air. Consequently, the wiring materials are corroded thereby, resulting in an increase in electric resistance and wire breakage, thus causing serious adverse influeneces.
As a method for preventing such corrosion of the wiring materials, a method is put into practice for example, in which said radicals and ions are washed away by carrying out a cleaning treatment with ultrapure water for a long time after the dry etching. In this method, however, it is extremely difficult to completely remove the radicals and ions from the deposit polymer formed and stuck to the side walls and there is always a fear of causing corrosion of the wiring materials. It is therefore indispensable to completely remove the deposit polymer for the purpose of exterminating the corrosion.
In addition, it is difficult to remove the deposit polymer formed in the case of a dry etching treatment for the layer of titanium or tungsten. Although such deposit polymer is removable by a cleaning treatment through the use of a treating liquid containing hydrofluoric acid or containing hydrofluoric acid and ammonium fluoride, a metallic layer made of tungsten, titanium, an alloy thereof, titanium/tungsten alloy, titanium nitride or the like has fair corrosion resistance against a fluorine compound, but has not complete corrosion resistance thereagainst, thereby causing a fear that the electrical reliability is lost by pattern peeling and the like. The deposit polymer, when being allowed to remain unremoved, causes adjacent wirings to come into contact therewith by the accumulated pressure of the film in the next step, thus giving rise to a short circuit and an abnormality of wiring.